diagnostics
ArticleRoutine Fluorescence Imaging to Detect Wound Bacteria
Reduces Antibiotic Use and Antimicrobial Dressing
Expenditure While Improving Healing Rates:
Retrospective Analysis of 229 Foot Ulcers
Nadine Price
Podiatry—Gillian Hanson Diabetes Centre, Whipps Cross Hospital, Waltham Forest ICD, North East London
NHS Foundation Trust, London E11 1NR, UK; nadine.price2@nhs.net
Received: 28 October 2020; Accepted: 7 November 2020; Published: 10 November 2020


Abstract: Foot ulcers and their bacterial burden produce a significant strain on the National
Healthcare System (NHS). Subjectivity of wound infection assessment makes appropriate dressing
selection challenging. To aid point-of-care detection of bacterial burden, a fluorescence imaging device(MolecuLight i:X) was introduced to the Whipps Cross Hospital Podiatry clinic. This retrospective
pre/post-analysis evaluated how implementation of fluorescence imaging impacted (1) antimicrobial
dressings and antibiotics use and (2) wound healing rates. Over a 2-year period 229 lower extremity
wounds were treated. Wound-related outcomes and antimicrobial dressing costs were quantified over
1-year before (2018/2019) and after (2019/2020) incorporating fluorescence imaging into routine practice.
The period of fluorescence imaging saw a 27% increase in the number of wounds seen, yet annual
antimicrobial dressing expenditure decreased by 33%. Implementation of fluorescence imaging was
also associated with a 49% decrease in prescription of antimicrobial dressings, a 33% decrease in
antibiotic prescriptions, and a 23% increase in wound healing rates within 12-weeks (48% vs. 39%),
likely due to earlier bacterial detection and improved wound hygiene. This increased healing rate
is projected to decrease annual wound costs by 10% (£762 per patient). Routine bacterial imaging
appears to diminish clinical and economic burden to patients and the NHS.
Keywords: dressing selection; diabetic foot ulcer; antimicrobial; fluorescence imaging; woundassessment; bacteria; MolecuLight

1. Introduction
Diabetic foot ulcers (DFUs) are relatively common complications of diabetes. Diabetes may
result in microvascular and macrovascular damage, along with neuropathy that frequently leads tonon-healing ulcers [1,2]; up to 7% of people living with diabetes in the UK currently have or have had
a foot ulceration [3]. DFUs are typically chronic wounds, with some ulcers persisting for months whileothers never heal or lead to amputation. Five-year mortality rate of individuals with diabetic footulceration is as high as 40% [4]. Management and care of these complex wounds produces a significant
strain on the healthcare system.
Diabetic foot ulcers represent a large and ever-increasing financial burden on the National HealthService (NHS). A recent study estimated the cost to treat diabetes-induced ulceration and amputation
in England in 2014–2015 at £837–£962 m annually [5]. This is equivalent to almost £1 in every £100
spent by the NHS in England and is higher than the estimated NHS expenditure on breast, prostate,
and lung cancers combined [6]. Approximately 90% of diabetic foot care costs in England are related
to ulcers; average foot ulcer cost to the NHS was £7800 annually in 2018 [7]. Healing time is thelargest driver of this cost [7]. With prolonged wound duration, more resources are required to manage
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the wound. Among them, antimicrobial dressings used to manage bacterial burden in these complex
wounds account for approximately £110 million per year spent in primary care in England, with morethan £20 million spent on silver dressings alone [8]. With frequent government cuts in budgets and
NHS spending, clinical managers and clinicians are encouraged to seek ways to help reduce costs andcontrol health care budgets while still providing safe and effective care for patients.
Current evidence-based practice for management of diabetic foot ulcers recommends that treatment
selection be based on assessment of signs and symptoms of wound infection, along with information
about the personal experiences and preferences of the patient. Infection classification systems suchas those produced by the International Working Group on the Diabetic Foot (IWGDF) [9] have beendeveloped to help characterise and guide infection management. However, these clinical signs andsymptoms of infection are subjective and can go undetected and are often lacking in wounds withhigh bacterial loads [10], causing delays in diagnosis and appropriate treatment. As such, assessment
and dressing selection remain primary clinical challenges in wound management [11,12]. Suboptimalassessment contributes to delays in wound healing and wasted resources [13]; alternative solutions
that guide treatment by providing objective diagnostic information at the point-of-care are required toenhance dressing selection and improve patient outcomes.
The MolecuLight i:X fluorescence imaging device (MolecuLight Inc. Toronto, Canada) is a
handheld non-contact imaging device that aids in identification of wounds with high bacterial load.
The device emits a safe violet light that enables visualisation of fluorescence produced by bacteria andtissues [14]. The presence of red or cyan fluorescence provides information on clinically relevant levelsof bacteria (>104 CFU/g) in and around the wound; this information can be used to target cleaningand debridement [15]. The real-time information on wound bioburden provided by fluorescenceimaging can address diagnostic uncertainty and ensures judicious selection of wound dressings or useof antibiotics.
The diabetic foot team at Whipps Cross University Hospital have been using fluorescence imaging
in clinic for over 12 months as part of routine standard clinical care. Both clinician and patient
experiences have been very positive, but we were particularly interested in evaluating how theaddition of real-time fluorescence imaging to the standard wound assessment impacted: (1) use of
antimicrobial dressings, as this represents our highest cost burden in relation to dressing expenditureand (2) healing rates, the highest drivers of wound costs within the NHS. In this retrospective
observational pre/post-intervention analysis, we aimed to evaluate how the addition of fluorescenceimaging to standard wound assessment impacted dressing selections and antibiotic prescriptions forcomplex foot wounds over a two-year period, and whether 12-week healing rates were impacted.
2. Materials and Methods
2.1. Standard of CareAll patients received care in line with the NICE clinical guideline NG19 [16] as a basic minimum.
This included appropriate offloading, infection management, metabolic control support, wound
management, and vascular assessment (doppler ultrasound). Patients also had access to themulti-disciplinary team which includes a vascular surgeon, diabetologist, podiatrist and microbiologist
as and when necessary depending on their clinical need.
2.2. Fluorescence Imaging Procedure
The handheld fluorescence imaging device (MolecuLight i:X, MolecuLight Inc. Toronto, Canada)visualises bacteria in the wound and peri-wound using 405nm wavelength safe violet light [14].
Fluorescence is detected from 28 common wound pathogens and is also detected from bacteria
within biofilms [17]. Red fluorescence is detected from porphyrin producing-bacteria (most wound
pathogens [17]) while pyoverdine-producing bacteria such as Pseudomonas aeruginosa are associatedwith a cyan fluorescent signal [18]. Red or cyan fluorescence signals are indicative of bacteria at loads

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Diagnostics
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10, 927
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witha cyansignal [18]. Red or cyan fluorescence signals are indicative of bacterialoadsa >cyan
104 fluorescent
CFU/g (moderate
to heavy[10,14,19]. The
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imagingaredisplayedonadigitaltouch
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identify
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determine
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foot ulceration,
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and 2 show examples of red and cyan fluorescing bacteria in diabetic foot ulceration, Figure 2 also
bacterial
fluorescencefootulceration,
Figure 2imaging.
also details the microbiology results following guided tissue sampling using
details the microbiology results following guided tissue sampling using bacterial fluorescence imaging.
bacterial fluorescence imaging.

Figure 1. Cyan fluorescing bacterium (white arrows) indicating Pseudomonas aeruginosa on a diabetes
Figure1. Cyanfluorescing
bacterium(whitearrows) indicating
Pseudomonas
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diabetes
foot
ulcer
overlyinga midfootCharcot
footarrows)
deformitywith subsequent
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imaging
Figure1. Cyanfluorescing
bacterium(whiteindicating
Pseudomonas
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foot
ulcer
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Charcot
foot
deformity
withsubsequent
standard
imaging
showingthethe ulcer
wound
fully healed
12 weekslater. foot deformity with subsequent standard imaging showing
footoverlyinga midfootCharcot
wound fully healed 12 weeks later.
the wound fully healed 12 weeks later.

Figure 2.
2. 34-year-old
34-year-oldmale
malewith
withextremely
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poorlycontrolledcontrolledtype
type11 diabetes
diabetespresented
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to thethe foot
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with
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Streptococcus,+Coagulase-negative
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intravenous
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theappropriate
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debridement
approximately 5 days later but went on to make a full recovery with no further
complications.

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Real-time detection of fluorescence signals indicative of clinically significant levels of bacteria
Real-time detection of fluorescence signals indicative of clinically significant levels of bacteria
can help a clinician evaluate whether an antimicrobial dressing should be included as part of the
can help a clinician evaluate whether an antimicrobial dressing should be included as part of thetreatment plan. Figure 3 describes a clinical decision tree that uses information provided bytreatment plan. Figure 3 describes a clinical decision tree that uses information provided by fluorescence
fluorescence imaging to inform clinical decision making. This has become the standard of care at ourimaging to inform clinical decision making. This has become the standard of care at our site sincesite since incorporating fluorescence imaging. Table 1 describes the criteria for using fluorescence
incorporating fluorescence imaging. Table 1 describes the criteria for using fluorescence imaging.
imaging.

Review patient
history and perform

Capture fluorescence
image

standard of careassessment
Is red or cyan (bacterial)
Nofluorescence present? inYes

the wound?

Capturefluorescence image

bacterial signal

to regions of bacteria
in woundIs red or cyan (bacterial)

Debridement
eliminatedTarget debridementNo

fluorescence present? inthe wound?

Bacteria deep in theYestissue could indicate
local infection

Select antimicrobial

Collect sample fromdressing to manage

region of red or cyanbacterial burden.

fluorescence

Proceed with selectionof dressing andoffloading as required

Choose antibiotics, only
if warranted, based on
sampling results.

Figure3. Thisdecisiontree
describes
imaginginformation
information
impactedtreatment
Figure3. Thisdecisiontree
describeshow
how fluorescence
fluorescence imaging
impactedtreatment
selection.
selection.
The presenceof redcyan fluorescence,
fluorescence, indicative
moderate-to-heavy
bacterialload,load,
The presenceof redororcyan
indicativeofof
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afterafter
debridement,
prompted
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or woundsampling,asdebridement,
prompted
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additional
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or woundsampling,
needed.
Fluorescence
information
informed
dressing
selection.
Antibiotics
were wereprescribed
only only
if if
as needed.
Fluorescence
information
informed
dressing
selection.
Antibiotics
prescribedindicatedfromfrom
sampling
results
exceptin cases
where
therethere
werewereotherotherclearclear
signssigns
or symptoms
of ofindicatedsampling
results
exceptin caseswhereor symptoms
infection
present.
infection
present.

Diagnostics 2020, 10, x FOR PEER REVIEW
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Diagnostics 2020, 10, x FOR PEER REVIEW
5 of 11
Diagnostics 2020, 10, 927
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Diagnostics 2020, 10, x FOR PEER
REVIEW
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1. Criteria for using bacterial fluorescence imaging.
Diagnostics 2020, 10, x FOR PEER
REVIEW
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1. Criteria for using bacterial fluorescence imaging.
 2020,
Suspected
soft
tissueinfection(e.g.,
presenceof 2 or moreimaging.
symptoms according to 5 of 11
Diagnostics
10, x FOR PEER
REVIEW
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1.
Criteria
forusingbacterial
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Table 1. Criteria for using bacterial fluorescence imaging.
 2020,
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antimicrobial
dressings
added
to
the
formularyoverthenon-prescription
ordering
servicereports.
The
data
regardingpatient
demographics,
healing
rates
andantibiotic
prescriptions
wereextracted
fromourelectronic
recordkeeping
database.
Althoughtheclinicprimarily
providestreatmentforthosepatients
withdiabetes,anon-wound
small
percentage
offromthecaseload
included
in2.
the
data
analysiswerepatients
withextremity
woundsoriginating
othercausesi.e.,
limb
ischemia.
Patients
who
attended
thelower
clinicforextracted
otherreasons(e.g.,
Charcot
monitoring
andassociatedtreatment)
were
excluded.
The
antimicrobial
dressings
includedaredenoted
Year
The
data
on
dressing
expenditurewasfrommonthly
onlinetwo-yearperiod.
andantibiotic
prescriptions
wereextracted
fromourelectronic
recordkeeping
database.
Althoughtheclinicprimarily
providestreatmentforthosepatients
withdiabetes,asmall
percentage
ofthecaseload
included
in
the
data
analysiswerepatients
withlower
extremity
woundsoriginating
from
other
causesi.e.,
limb
ischemia.
Patients
who
attendedtheclinicforothernon-woundreasons(e.g.,
Charcot
monitoring
andtreatment)
were
excluded.
The
antimicrobial
includedinthe analysis
were
all associatedeithersilveror iodine-based
dressings.
There
were no dressings
new antimicrobial
non-prescription
ordering
servicereports.
The
data
regardingpatient
demographics,
healingrates
theclinicprimarily
providestreatmentforthosepatients
withdiabetes,asmall
percentage
ofthecaseload
included
in
the
data
analysiswerepatients
withlower
extremity
woundsoriginating
from
other
causesi.e.,
limb
ischemia.
Patients
who
attendedtheclinicforothernon-woundreasons(e.g.,
Charcot
monitoring
andassociatedtreatment)
were
excluded.
The
antimicrobial
dressings
included
in
the
were
allformulary
eithersilverorthe
iodine-based
dressings.
There
were nodatabase.
new antimicrobial
3.analysis
Results
dressings
addedto theover
two-yearandantibiotic
prescriptions
wereextracted
fromourperiod.
electronic
recordkeeping
Althoughcaseload
included
in
the
data
analysiswerepatients
withlower
extremity
woundsoriginating
from
other
causesi.e.,
limb
ischemia.
Patients
who
attendedtheclinicforothernon-woundreasons(e.g.,
Charcot
monitoring
andassociatedtreatment)
were period.
excluded.
TheThere
antimicrobial
includedintheanalysis
wereallformulary
eithertreatment
silverorthe
iodine-based
dressings.
were
no dressingsnew
antimicrobial
dressings
addedto theover
two-yeartheclinicprimarily
providesfor
thosepatients
withdiabetes,anon-wound
small
percentageof(e.g.,theothercausesi.e.,
limb
ischemia.
Patients
who
attendedtheclinicforotherreasons
Charcot
monitoring
andassociatedtreatment)
were
excluded.
The
antimicrobial
dressings
includedintheanalysis
werealleithersilveroriodine-based
dressings.
There
were
no
new
antimicrobial
3.1.
Patient
Demographics
andThroughput
dressings
added
to
the
formularyoverthetwo-yearperiod.
3.
Results
caseload
included inandthe associateddata analysis
were patientswith lowerTheextremity
wounds originatingfrom
Charcot
monitoring
treatment)
were period.
excluded.
antimicrobial
includedinthe analysis
either silver
orthe
iodine-based
dressings. There
were no dressings
new antimicrobial
dressings
addedwereto theallformulary
over
two-year3.
Resultsothercausesi.e.,
limb
ischemia.
Patients
who
attendedtheclinicforothernon-woundreasons(e.g.,
Inthe12
months
prior
to
use
of
the
fluorescenceimaging
procedure
fordetectionofbacteria,
intheanalysis
wereeithersilveriodine-based
dressings. There were no new antimicrobial
dressings
addedto theallformulary
overorthe
two-year period.
3.
Results
3.1.
Patient
Demographics
andThroughput
Charcot
monitoring
andassociatedtreatment)
were
excluded.
The
antimicrobial
dressings
included
92% of patients
had diabetes,
average ageof patients was 58.4 years old and more male thandressings
to thetreatedformularyover the two-year
period.
3.
3.1.Results
Patientadded
Demographics
and Throughput
inthe
analysis
werealleithersilveroriodine-based
dressings.
There
were
no
antimicrobial
femalepatients
weretreated(51/21);(Table2).
Averagepatient
age and
ratio
ofnew
male
to
patientsInthe12
months
prior
to
use
of
the
fluorescenceimaging
procedure
fordetectionof femalebacteria,
3. Results
3.1.
Patient Demographics and Throughput
In
the
12
months
prior
to
use
of
the
fluorescenceimaging
procedure
fordetectionofbacteria,
dressings
added
to
the
formularyoverthetwo-yearperiod.
remainedsimilarbetween
years
1
and
2,
while
percentageofpatients
withdiabeteswasslightly
92%of patientstreated had
average age of patients was 58.4 years old and more male than lower
3.
Results
3.1.
Patient
Demographics
anddiabetes,
Throughput
In
the
12
months
prior
to
use
of
the
imaging
procedure
fordetectionofmale92%
ofinpatientstreatedhaddiabetes,
averageageof patients
was
58.4
old
and
more
than wereyear
2 compared
to Year1 (83%
vs.fluorescence92%).
analysis
found
that
27%
more
woundsfemalepatients
were treated(51/21);(Table2). Retrospective
Averagepatient
ageyears
and
ratio
of
male
tobacteria,
female
3.1.
Patient
Demographics
andThroughput
In
the
12
months
prior
to
use
of
the
fluorescenceimaging
procedure
fordetectionof92%
oftreatedpatients
haddiabetes,
averageageofwhilepatients
wasand58.4
years
oldpatients
and
male
than
3.
Results
femalepatients
were(51/21);(Table2).wounds
Averagepatient
age
and
ratio
of moremale
tobacteria,
femalein treatedYear
2 treatedcomparedto Year
1 1(128
vs.percentage
101)
7%
more
received
treatment
3.1.
Patient
Demographics
andThroughput
patients
remainedsimilarbetween
years
and
2,
of
patients
withdiabeteswas
In patientsthe
12 months
prior
to(51/21);
use ofthefluorescenceimaging
procedure
fordetectionofmalebacteria,
92%oftreatedhaddiabetes,
averageageofpatients
was
58.4
years
old
and
more
than
femalepatients
weretreated(Table2).
Averagepatient
age
and
ratio
of
male
to
femalepatients
remainedsimilarbetween
years
1
and
2,
while
percentageofpatients
withdiabetes
was
(77
vs.
72),
despitesimilarcliniccapacity,
i.e.,
hours
and
staffing.
slightly lower in year 2 compared to Year 1 (83% vs. 92%). Retrospective analysis found that 27%
In patientsthe
12 months
prior
touse ofthefluorescenceimaging
procedure
fordetectionofmalebacteria,
92%oftreatedhaddiabetes,
averageageofpatients
was
58.4
years
old
and
more
than
femalepatients
weretreated(51/21);(Table2).
Averagepatient
age
and
ratio
of
male
to
female
3.1.
Patient
Demographics
andThroughput
patients
remainedsimilarbetween
years
1
and
2,
while
percentageofpatients
withdiabeteswasslightly
lower werein year2 comparedYear 1 (83%vs. 92%).
Retrospective
analysisfound27%
more wounds
treatedin Year2tocompared
to Year
1 (128woundsvs. (Year
101)
and
7%
morethatpatients
Table treated
2.wereRetrospective
analysisof 12 months
before(Year1) andafter2)and
implementing
routine92%ofpatients
haddiabetes,
averageageofpatients
was
58.4
years
old
more
male
than
femalepatients
treated(51/21);(Table2).
Averagepatient
age
and
ratio
of
male
to
femalepatients
remainedsimilarbetween
years
1
and
2,
while
percentageofpatients
withdiabeteswasslightly
lower
in year2priortocompared
Yearfluorescence
1 (83%
vs.
92%).
Retrospective
analysis
found
that
27%
moreInwounds
treated
intoYear2ofto Year1imaging(128i.e.,wounds
101)
and
7%
more
patients
received
treatment(77
vs.compared72),
despitesimilarcliniccapacity,
hoursvs.
andstaffing.
the12 weremonthsuse
theprocedure
fordetection
oftobacteria,
fluorescenceimagingofbacteria
intothepodiatryclinic.
femalepatients
weretreated(51/21);(Table2).
Averagepatient
age
and
ratio
of
male
femalepatients
remainedsimilarbetween
years
1
and
2,
while
percentageofpatients
withdiabeteswasslightly
lower
in year
2vs.comparedYear 1 (83%
vs.
92%).
Retrospective
analysis
found
that
27%
more
were
treatedinYear
2tocompared
to of
Year
1 (128waswounds
vs.
101)
7%
more
patients
received
treatment(77
despitesimilarcliniccapacity,
i.e.,
hours
and
staffing.
92%
ofwounds
patients
treatedhad72),
diabetes,
averageagepatients
58.4 ofyears
oldand
and
more
male
than
patients
remainedsimilarbetween
years
1
and
2,
while
percentage
patients
withdiabeteswasslightly
lower
in year
2vs.comparedto months
Year 1 before
(83%
vs.
92%).
Retrospective
analysis
found
that
27%
moreTable
woundsweretreatedin Yearto Year
1 (128woundsvs.
101)
and2 7%
more
patients
received
treatment(77
72),
despitesimilarcliniccapacity,hours
andstaffing.
Year
1 i.e.,
Year
2. Retrospective
analysisof 212compared(Year1) patient
and
after
(Year
2)
implementing
routinefemalepatients
weretreated(51/21);(Table2).
Average
age
and
ratio
of
male
to
femaleslightly
lower
in year
2vs.comparedYear 1 before
(83%
vs.
92%).
Retrospective
analysis
found
that
27%
moreTable
woundsweretreatedin Year
2to
to12
Year
1 (128woundsvs.
101)
and 7%
more
patients
MonthsPrior
to12Monthsreceived
treatment(77
72),
despitesimilarcliniccapacity,
i.e.,
hours
and
staffing.
2. Retrospective
ofinto12comparedmonths(Year1) and
after
(Year
2)
implementing
routinefluorescenceimagingofanalysis
bacteria
the podiatry
clinic.
patients
remainedsimilarbetweenyears
1 andto2,Year
while
percentageofpatients
withdiabeteswasmoreTable
woundsweretreatedinYear2compared1(128
wounds
vs.
101)
and
7%
more
patients
Fluorescence
Post-Fluorescence%
Changereceived
treatment
(77
vs.
72),
despitesimilarcliniccapacity,
i.e.,
hours
and
staffing.
2. Retrospective
12 months
before(Year 1) and after (Year 2) implementing routine
fluorescenceimaging ofanalysis
bacteriaofinto
the podiatry
clinic.
slightly
lower
in
year
2
compared
to
Year
1
(83%
vs.
92%).
Retrospective
analysis
found
that
27%
of andBacteria
Imaging
1 ImagingYear
2 of Bacteriaroutine
received
treatment(77 vs.
72),
despitesimilarcliniccapacity,
i.e.,
hours
and
staffing.
Table
2. Retrospective
ofinto12 months
before(Year 1)
after
(Year
2) implementing
fluorescenceimagingofanalysis
bacteria
theYearpodiatryclinic.
(2018/2019)(2019/2020)
moreTable
woundsweretreatedinYear2compared
to
Year
1
(128
woundsvs.
101)
patients
Year
1
Year
2 and 7% more
12
MonthsPrior
to12Months
2. Retrospective
12 months
before(Year 1) and after (Year 2) implementing
routinefluorescenceimaging ofanalysis
bacteriaofinto
the podiatry
clinic.
%
Year
2
Year
1
received
treatment
(77
vs.
72),
despitesimilarcliniccapacity,
i.e.,
hours
and
staffing.
12MonthsPrior
to12MonthsPatient
demographics
Table
2. Retrospective
ofinto12 months
before(Yearafter (Year 2) implementing
Fluorescence
Imagingof 1) and
Post-Fluorescence
Imaging routine
fluorescenceimaging ofanalysis
bacteria
the podiatry
clinic.
%ChangeYear
1 clinic.
2 Imaging
12 Months
Prior
to of58.4 Post-Fluorescence
12YearMonthsFluorescence
Imaging
fluorescenceimaging
intothepodiatry
Bacteria
ofBacteria
Average patient
ageof bacteria
60.1
ChangeYearImaging
1
2 Imaging routine%Prior
to
12YearMonthsTable
2. Retrospective analysis
of1212Months
monthsbefore(Year1) andafter (Year2) implementing
Fluorescenceof51/21
Post-Fluorescence
Bacteria
ofBacteria
Male/Female
50/27(2018/2019)(2019/2020)%
Change2 83%
Year
1 clinic.
12 Months
Prior
to of92% Post-Fluorescence
12YearMonthsfluorescenceimagingbacteria
intothepodiatry
Fluorescence
Imaging
Imaging% of patientswith ofdiabetes
Bacteria
ofBacteria(2018/2019)(2019/2020)
Patient demographics%
Change12 Months
Prior to of101 Post-Fluorescence
12 Bacteria
MonthsImaging
Imaging# of wounds seen in clinic Fluorescence
128
Bacteria
of(2019/2020)(2018/2019)
Patient
demographics%+27%
ChangeAveragepatient age
58.4Imaging
60.12 77
Year
Year
1
# of patients+7%
Fluorescenceof 72 Post-Fluorescence
Imaging
Bacteria
ofBacteria(2018/2019)(2019/2020)
Patient
demographics
ChangeAveragepatient age
58.4Prior
60.1
Male/Female
51/21
50/27
12 Months
to12 Bacteria
MonthsBacteria
of(2018/2019)(2019/2020)%
Patient
demographics
Averagepatient
agediabetes Fluorescence
58.4Imaging
60.1 Imaging
Male/Female
51/21
50/27
% of patients
with
92%
83%
of
Post-Fluorescence(2019/2020)(2018/2019)
Patient
demographics
ChangeAveragepatient
age
58.4
60.1
Male/Female
51/21
50/27
%
ofwounds
patientsseen
withindiabetes
92%
83%
# of
clinic101128+27%
Bacteria
of Bacteria
Patient
demographics
Averagepatient
age
58.4
60.1
Male/Female
51/21
50/27
%
of
patients
withdiabetes
92%
83%# of patientswounds seen in clinic
101
128
+27%
72
77
+7%
(2019/2020)(2018/2019)
Averagepatient
age
58.4
60.1
Male/Female
51/21
50/27
%
ofpatientspatients
with
92%
83%
woundsseen
indiabetes
clinic
101
128
+27%
# of
72
77
+7%
Patient
demographics
Male/Female
51/21
50/27
%
ofpatientspatientsseen
withindiabetes
92%
83%
# of
woundsclinic
101
128
+27%
72
77
+7%
Averagepatient
agediabetes
58.4
60.1
%
ofpatientspatients
with
92%
83%
woundsseen
in clinic
101
128
+27%
# of
72
77
+7%
Male/Female
51/21
50/27
# of patientswounds seen in clinic
101
128
+27%
72
77
+7%
%
ofpatientspatients with diabetes
92%
83%
# of
72
77
+7%
# of wounds seen in clinic
101
128
+27%

Diagnostics 2020, 10, 927

6 of 11

Table 2. Cont.
Year 212 Months
Post-Fluorescence
Imaging of Bacteria(2019/2020)% Change£2,291

£1531

−33%

£22.68£11.96

−47%

39%

48%

+23%

67%

45%

−33%

85%

44%

−49%

18%

16%

−11%

Year 1
12 Months Prior to
Fluorescence
Imaging of Bacteria(2018/2019)
Outcomes and expenditures
Antimicrobial dressing expenditure
Antimicrobial spending normalised to #of wounds% of wounds healed within 12 weeks% of patients who required antibiotics fortheir wound% of patients prescribed
antimicrobial dressings% of patients requiring an amputation# refers to number of wounds.

3.2. Antimicrobial and Antibiotic Usage and 12-Week Healing Rates
Baseline data from year one revealed that 39% of wounds treated in the clinic healed within
12 weeks (Table 2). Two thirds of patients were prescribed antibiotics to manage wound infection
at some point during their care, and 85% of patients were prescribed antimicrobial dressings tomanage infection and high bacterial burden. During this 12-month period, 18% of patients had awound-related amputation.
In Year 2, incorporation of the fluorescence imaging procedure as part of routine wound care
(Figure 3) was associated with a 33% decrease in the percentage of patients requiring antibiotic
prescription compared to the previous year. This was not associated with an increased relianceon antimicrobial dressings, as the percentage of patients prescribed these dressings decreased by anotable 49%. This decrease in antimicrobial usage coincided with a 23% increase in proportion ofwounds that healed within a 12-week period (48% in Year 2 vs. 39% in Year 1), and an 11% decreasein patients requiring amputation over the course of Year 2 (16% vs. 18%). This suggests that earlier
bacterial detection through routine imaging combined with wound hygiene interventions was aneffective diagnostic and treatment pairing in this population.
3.3. Antimicrobial Expenditure
The fluorescence imaging procedure was introduced into the diabetic foot clinic in April 2019.
In the 12 months prior to this (2018/19) the total expenditure on antimicrobial dressings was £2291(Table 2). A 33% reduction in antimicrobial dressing expenditure (£1531) was observed in the 12 months
after the fluorescence imaging procedure was incorporated as part of standard practice when assessing
wounds. This occurred despite a 7% increase in patient volume and 27% increase in the total numberof wounds treated over the course of the year in which the fluorescence imaging procedure wasintroduced and utilised (Table 2). To account for the difference in number of wounds treated overthe course of 2 years, antimicrobial spending was normalised by the number of wounds treated.
Per wound, antimicrobial spending fell by 47% from £22.68 to £11.96 after introduction of point-of-carebacterial fluorescence imaging into routine practice.
3.4. Estimating Impact of Healing Rates on Total Wound Care Expenditure
To estimate the impact of routine fluorescence imaging on total annual wound care costs per patient,
the observed healing rate data from Year 1 and Year 2 was multiplied by the known costs of woundcare reported by Guest et al. [7]. Their analyses, based on a retrospective study of 130 DFU patients,
reported the mean cost to the NHS of care for a foot wound over 12-months to average £7800. This cost

Diagnostics 2020, 10, 927

7 of 11was driven largely by the healing rate over a 12-month period; the cost of care for an unhealed foot ulcer(£8786) was found to be 4 times higher than that of a healed foot ulcer (£ 2138), while wounds resulting
in amputations cost the NHS £16,941 annually on average. These varying costs were applied to theempirical healing rates observed in Year 1 and Year 2 to estimate the impact of fluorescence imaging on
total NHS wound expenditure in this patient population (Table 3). This modeling incorporates theamputation rates observed in year 1 and 2 and assumes the 12-week healing rates observed in Years 1
and 2 were consistent over 12 months.
Table 3. Estimated annual total cost of wound care before (Year 1) and after (Year 2) implementation of
the fluorescence imaging procedure.

Estimated cost [7]Year 1standard of careYear 2standard of care +fluorescence imaging
Estimated cost savings
per patient

Healed Foot Ulcer

Amputated Foot
Ulcer

Unhealed Foot
Ulcer

Total Cost of Wound Care
(Annual per Patient)£2138£16,941

£8786

39%

18%

43%

£7662

48%

16%

36%

£6900

£762

In Year 1, with 39% of wounds healed within 12-weeks, the 12-month total wound care costs
were computed to average £7662, similar to the 12-month average cost of wound care reported
by Guest et al. [7]. In Year 2, the 23% increase in healing rates resulted in estimated total cost ofcare averaging £6900 per wound, a 10% decrease in costs (savings of £762 per wound). Given that128 wounds were treated over the course of Year 2, the total annual Year 2 savings is estimatedat £97,536.
4. Discussion
Prescription of antimicrobial dressings in the UK has steadily increased in the last two decades [20],due in part to uncertainty relating to detection of bacterial burden in wounds. High bacterial burden
is well established to delay healing [21,22]. More objective methods to detect wound bacterial
burden during wound assessment may facilitate judicious use of antimicrobials and antibiotics [23].
In this study, we conducted a retrospective analysis to evaluate how routine use of fluorescence imaging,which detects elevated bacterial burden in wounds at point-of-care, impacted dressing selection andwound outcomes. To our knowledge, this is the first retrospective study reporting healing rates anddirect cost savings associated with use of fluorescence imaging.
A decrease in the proportion of patients prescribed antimicrobial dressings (−49%) and antibiotics(−33%) was observed with routine use of fluorescence imaging in Year 2. The reason for this could not
be conclusively determined in this retrospective analysis. However, it is speculated that this decrease,
as well as the improved healing rates, is due in large part to earlier detection of wound bacteria at a stage
when bacterial burden could be effectively eliminated through mechanical removal (e.g., debridement).
Debridement, which effectively removes dead and bacteria-laden tissue, is standard of care and essential
to wound healing; wounds debrided more frequently heal more rapidly [24], and frequent debridement
is needed to disrupt bacterial biofilms [25,26]. It is not surprising, therefore, that targeting debridement
to regions of red (bacterial) fluorescence is associated with faster wound area reduction rates [27].
Larger studies on healing impact of routine fluorescence imaging have been lacking, though clinical
trials have reported that fluorescence images impacted the extent of debridement in greater than 50%
of wounds, due to detection of bacteria that was missed by standard care [10,19]. In each of thosestudies, the improvements were attributed to fluorescence images alerting the wound care provider toboth: (1) the presence of clinically significant levels of bacteria in wounds that fall below the infection
threshold or (2) infected but asymptomatic wounds. Early detection of bacteria in wounds prior to
escalation to levels of infection is essential to ensure timely healing [28]. This is especially relevantDiagnostics 2020, 10, 927

8 of 11among individuals with diabetes, which make up a large portion of our patient population. Often,
patients with diabetes have heavily bioburdened or infected foot ulcers [29], yet frequently fail tomount the classic signs and symptoms of infection [30]. This highlights the importance of a moresensitive [10,14] and objective method of detecting bacterial burden in wounds. In this study, given thatthe patient characteristics between Year 1 and Year 2 were consistent, it is unlikely that the increased
healing rate and decreased need for antimicrobials were due to dramatic changes to the severity ofwounds seen in the clinic in Year 2. Therefore, our analysis strongly suggests that routine use offluorescence imaging resulted in overall improved wound management and wound outcomes.
Wound care has been flagged as a major contributor to antibiotic over prescription andresistance [23]. Antimicrobial resistance is a significant issue in the UK and worldwide that continues
to have devastating consequences on human health and the economy. In response to this threat,leading healthcare committees and societies from around the world [31,32] have called for improved
strategies to optimise antimicrobial use. This remains a challenge in wound care due to continued
reliance on subjective and variable measures of wound infection to guide antimicrobial decision making.
This, combined with an increased susceptibility of wound infection among diabetic patients [29],and clinician fear of missing the infection, has driven increased use of antimicrobial dressings [20].
To reduce unnecessary use of antimicrobials, wound care stewardship guidelines have therefore called
for more objective methods to detect bacterial burden at the bedside [23]. Our analysis reveals thatroutine use of fluorescence imaging for detection of bacterial burden at point of care is associated with
reductions in both antibiotic and antimicrobial usage, suggesting that over prescription was decreasedin favor of mechanical strategies, such as debridement, to manage bacterial burden. The absenceof fluorescence from bacteria in fluorescence images enhanced confidence that an antimicrobial
dressing may not be needed, where previously, a clinician may have made that decision based
solely on clinical assessments. The same can also be said of the opposite scenario, whereby highlevels of red/cyan fluorescing bacteria detected from a wound that did not appear to be clinicallyinfected prompted sampling to be done from the region of bacterial fluorescence and selection of an
antimicrobial dressing. In many instances, topical antimicrobials were utilised instead of immediately
prescribing systemic antibiotics. This reduction in antimicrobial prescription was not at the detrimentof healing, indicating that the objective information provided by point-of-care fluorescence imaging
does indeed contribute to improved antimicrobial decision making.
Although there are a multitude of factors that contribute to the overall costs of treating complex footulcers, we chose to focus on the costs of antimicrobial dressing due to their increased use in recent years,
which undoubtedly has contributed to the rise in total wound care expenditures [20]. This increase isin part driven by the considerable variation in the type and costs of antimicrobial dressings available,
along with the relative lack of objective evidence to guide dressing selection. Results from our 2-year
retrospective analysis indicate that implementation of fluorescence imaging of bacteria as part ofroutine wound screening and monitoring substantially reduced costs associated with antibiotic andantiseptic dressing usage (by 33%), while simultaneously increasing wound healing rates. The observed
reduction in antimicrobial expenditure has tremendous significance for our site. However, it represents
less than 1% of the potential total cost savings to the NHS [7]. Wound healing rates impact manyfactors that contribute to the total costs of treating foot ulcers including clinical visits for routine care,
infection rates, laboratory tests, hospitalisation and amputations [2,33]. Our modeling reveals thatthe 23% increase in wound healing rate and 11% decrease in amputation rate observed with routine
use of fluorescence imaging contributes to a 10% decrease in total costs per patient, corresponding
to an annual cost savings to the clinic of £ 97,536 (based on assessment of 128 wounds per year).
Wound healing times are the largest driver of costs to the NHS, therefore strategies that enhance healing
rates are critical for cost containment; improving diagnosis of bacterial burden in the wound is key tothese efforts, based on the findings of this study.
In addition to these observed benefits to outcome and expenditure, it should be noted that patient
education and engagement during clinical visits was enhanced with the addition of the fluorescenceDiagnostics 2020, 10, 927

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imaging procedure and the subsequent images collected. These images are used to demonstrate clearly
the need for further diagnostic testing such as tissue sampling, imaging or blood tests, in addition to
the need for antibiotics when warranted and the importance of adhering to advice given and treatment
plans which are made. In our clinic, patients can see for themselves exactly where any bacteria may beat the wound site and are able to monitor, in subsequent visits, whether or not the wound is improving.
Studies assessing the impact of fluorescence imaging on patient education and engagement with theircare would be beneficial going forwards.
5. Strengths and Weaknesses
To the author’s knowledge, this retrospective analysis is the largest study of fluorescence imaging
of wound bacteria performed in the UK to date, and the first to compare wound healing rates andassociated costs between standard of care and fluorescence-guided care periods. There were minimal
exclusion criteria for the analysis and patient populations between Year 1 and Year 2 were fairly
consistent. Previous UK studies were observational in design, significantly smaller and looked
primarily at burn and trauma wounds, [15,34,35]. A recent NICE med tech innovation briefing [36]highlighted a need for large, UK-based multi-centre randomised controlled trials (RCT) comparing
MolecuLight i:X to standard of care within NHS settings. These trials are ongoing within the NHS(e.g., clinicaltrials.gov #NCT041875636).
There are limitations to this retrospective analysis. Most variables, other than fluorescence imaging
introduction to the clinic, were consistent across the 24-month evaluation period: staff was consistent,patient demographics were similar, and there were no other new technologies introduced. However,
we cannot discount the possibility that other factors may have played a role in the reduced expenditure(e.g., variability from the different patient cohort). The clinic primarily encounters foot ulcers, so it isunclear whether similar cost savings would be expected for clinics treating primarily venous leg ulcers.
The single centre nature of this study is a limitation, as is the type of data available for analysis;
multiple sites and larger patient numbers would be ideal. However, the year 1 data for both healing
and amputation rates was strikingly consistent with reports from other NHS facilities [7], suggestingthat our site is representative of the typical care provided for the treatment of foot ulcers.
6. Conclusions
Fluorescence imaging has proven to be a useful diagnostic procedure when examining andmanaging complex foot wounds at the point of care. It has undoubtedly helped with decision making,supporting discussions within the wider multi-disciplinary team. The positive impact on our dressing
expenditure for antimicrobials such as silver has been very welcome in the current climate and it has
supported the recommended two-week challenge for the use of silver dressings in the clinical setting.
Beyond these realised cost savings, the fluorescence imaging procedure has had a noticeable impact on
the quality of wound care provided to patients, without detriment to our clinical workflow. Having theability to know at point of care whether a wound has significant levels of bacteria that may be indicativeof infection enables us to offer the safest care for our patients and also provides instant clinical feedback
on treatment efficacy.
Funding: No funding was received for this study.
Conflicts of Interest: The author declares no conflict of interest.

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